Which of the following forces is correctly described about boiling point of Aldehydes & ketones -

Options

A. Hydrogen bond
B. Vander wall force
C. Dipole-dipole attraction
D. None of these

Answer

To determine which of the forces is correctly described about the boiling point of aldehydes and ketones, we will analyze the options provided: hydrogen bonding, van der Waals forces, dipole interactions, and none of these.

### Step-by-Step Solution:

1. **Understanding Aldehydes and Ketones**:
- Aldehydes and ketones contain a carbonyl group (C=O). The general structure for aldehydes is RCHO, and for ketones, it is R2C=O, where R can be an alkyl or aryl group.

2. **Analyzing Hydrogen Bonding**:
- Hydrogen bonding occurs when a hydrogen atom is directly bonded to a highly electronegative atom (like oxygen, nitrogen, or fluorine) and interacts with another electronegative atom.
- In aldehydes and ketones, the hydrogen atom is not directly bonded to the oxygen of the carbonyl group. Therefore, hydrogen bonding is not present in these compounds.

**Hint**: Check if hydrogen is directly bonded to an electronegative atom in the structure.

3. **Evaluating Van der Waals Forces**:
- Van der Waals forces are weak intermolecular forces that arise from temporary dipoles formed when electron distributions around atoms fluctuate.
- While van der Waals forces are present in aldehydes and ketones, they are not the primary force affecting their boiling points.

**Hint**: Consider the strength of intermolecular forces and their contribution to boiling points.

4. **Considering Dipole Interactions**:
- Aldehydes and ketones are polar molecules due to the presence of the carbonyl group, which creates a dipole moment (with a partial positive charge on carbon and a partial negative charge on oxygen).
- The dipole moments of these molecules can interact with each other, leading to dipole-dipole interactions. This interaction is significant in determining the boiling points of these compounds.

**Hint**: Look for the presence of polar bonds and how they affect molecular interactions.

5. **Conclusion**:
- Since aldehydes and ketones do not exhibit hydrogen bonding and van der Waals forces are not the primary contributors to their boiling points, the correct description of the forces affecting the boiling point of aldehydes and ketones is dipole-dipole interactions.

### Final Answer:
**Dipole-dipole interaction correctly describes the boiling point of aldehydes and ketones.**